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The effect of different reaction parameters helped in understanding the structure–property relationship in B-doped CNTs. A plausible reaction kinetic model and a reaction mechanism were proposed for the FCCVD synthesis of BCNTs.

Diglycolamic acid-functionalized carbon nanotubes were employed for the efficient and selective separation of Pu4+, PuO22+ and Am3+. The sorption occurred through monolayer coverage via chemisorption following the Langmuir isotherm. The sorption of Am3+, Pu4+ and PuO22+ on DGA-CNTs proceeded via a pseudo-second-order rate kinetics with a rate constant in the order Am3+ < Pu4+ < PuO22+. The radiolytic stability for DGA-CNTs and the stripping behaviour of DGA-CNTs were investigated. Luminescence investigations revealed the presence of single species without an inner-sphere water molecule. On complexation, the asymmetry around Eu3+ was found to be enhanced along with the covalency of the metal–ligand bond. Additionally, DFT calculations were performed to investigate the coordination and complexation interaction behaviour of CNT-DGA towards the metal ions. The present DFT study revealed a tridentate coordination mode of the DGA moiety towards Pu4+ and Am3+ and a bidentate coordination mode towards PuO22+. The calculated binding energy of sorption with DGA-CNTs towards Pu4+ was found to be higher than that of PuO22+, in both the gaseous and aqueous phase, whereas for Am3+, it was higher than that for PuO22+ but less than that for Pu4+. The free energy of sorption was also found to be highest for Pu4+ uptake and lowest for PuO22+, in both the gaseous and aqueous phase.

Amido amine-functionalized multi-walled carbon nanotubes (MWCNT-AA) were used for efficient and selective solid phase separation of plutonium(IV) and plutonium(VI). Langmuir, Freundlich, Dubinin–Radushkevich (D–R), and Tempkin isotherms were employed for understanding the sorption mechanism and Lagergren first order kinetics, an intra-particle diffusion model, and pseudo second order kinetics were applied to understand the sorption kinetics. The sorption proceeded through monolayer coverage of MWCNT-AA with capacities of 91.2 mg g−1 and 89.4 mg g−1 for Pu4+ and PuO22+, respectively following a Langmuir isotherm while the sorption kinetics followed a pseudo second order reaction with rate constants of 3.86 × 10−5 and 3.19 × 10−5 g mg−1 min−1 for Pu4+ and PuO22+ respectively. This MWCNT-AA showed high radiolytic stability and a method was developed for almost quantitative back extraction of plutonium in both the oxidation states from MWCNT-AA. Finally, the sorbent MWCNT-AA was employed for processing synthetic high level waste solution obtained from a research reactor origin. Moreover, density functional theory calculation was performed to examine the coordination and interaction behaviour of Pu4+ and PuO22+ ions towards MWCNT-AA. The present DFT study reveals that Pu is deca-coordinated (two from each of four nitrates and one AA) in the case of Pu4+ and octa-coordinated (two from each of two nitrates and one AA, and one from each of two oxo groups) in PuO22+. The calculated free energy of complexation was found to be almost three times higher for Pu4+ than PuO22+ both in the gas and aqueous phase, which thus confirms the experimentally observed higher sorption of Pu4+ compared to PuO22+ by MWCNT-AA.

Oleyl amine stabilised Pd nanoparticles have been prepared by reverse micro-emulsion method and supported on multi walled CNTs. TEM studies have confirmed that Pd nanoparticles, having sizes in the range of 3–5 nm, are well dispersed on the CNTs. Based on 13C MAS NMR and TG-DTA studies it is inferred that the Pd nanoparticles interact with CNT support to form sp3 carbon species, which get effectively dispersed on the CNTs. Such finely dispersed Pd nanoparticles facilitate the spillover of hydrogen to the CNT support and improve the hydrogen storage capacity.